U.S. patent number 6,351,439 [Application Number 09/269,917] was granted by the patent office on 2002-02-26 for method and system for managing access to data through data transformation.
This patent grant is currently assigned to International Business Machines Corporation. Invention is credited to Hiroya Kobayashi, Kunihiko Miwa, Norishige Morimoto.
United States Patent |
6,351,439 |
Miwa , et al. |
February 26, 2002 |
**Please see images for:
( Certificate of Correction ) ** |
Method and system for managing access to data through data
transformation
Abstract
In providing a system that can manage access to data to
effectively prevent illegal access to the data or the like, there
is provided a system for embedding access management information
that prepares management information for managing access to the
data, and embeds the management information in the data through
data transformation without changing amount of data. In managing
access to data, there is provided a method that extracts management
information embedded in the data through data deformation without
changing amount of data, and manages access to the data according
to the extracted management information. There is also provided a
method for changing management of access to the data according to
the type of medium in which the data is stored (RAM or ROM). The
management information further contains information for controlling
recording of the data, reception of the data, playback of the data,
interference of output of the data, duplication history of the
data, or modification of the management information. The access
management method can prevent illegal duplication of data or the
like, and can effectively protect a work.
Inventors: |
Miwa; Kunihiko (Hiratsuka,
JP), Kobayashi; Hiroya (Machida, JP),
Morimoto; Norishige (Tokyo-to, JP) |
Assignee: |
International Business Machines
Corporation (Armonk, NY)
|
Family
ID: |
17529399 |
Appl.
No.: |
09/269,917 |
Filed: |
April 1, 1999 |
PCT
Filed: |
August 12, 1997 |
PCT No.: |
PCT/JP97/02822 |
371
Date: |
April 01, 1999 |
102(e)
Date: |
April 01, 1999 |
PCT
Pub. No.: |
WO98/16928 |
PCT
Pub. Date: |
April 23, 1998 |
Foreign Application Priority Data
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|
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Oct 16, 1996 [JP] |
|
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8-273551 |
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Current U.S.
Class: |
369/47.18;
386/E5.004; 386/E9.013; G9B/20.002 |
Current CPC
Class: |
G06T
1/0035 (20130101); G11B 20/00086 (20130101); G11B
20/00094 (20130101); G11B 20/00768 (20130101); G11B
20/00884 (20130101); H04N 5/913 (20130101); H04N
9/8042 (20130101); G06T 2201/0051 (20130101); G06T
2201/0061 (20130101); G06T 2201/0064 (20130101); H04N
2005/91314 (20130101); H04N 2005/91321 (20130101); H04N
2005/91328 (20130101); H04N 2005/91335 (20130101) |
Current International
Class: |
G06T
1/00 (20060101); G11B 20/00 (20060101); H04N
9/804 (20060101); H04N 5/913 (20060101); G11B
007/00 () |
Field of
Search: |
;369/53.2,53.22,53.27,47.12,47.13,84,47.18,47.19 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
|
|
5-258463 |
|
Aug 1993 |
|
JP |
|
06-302092 |
|
Oct 1994 |
|
JP |
|
07-274115 |
|
Oct 1995 |
|
JP |
|
Primary Examiner: Hindi; Nabil
Attorney, Agent or Firm: Scully, Scott, Murphy & Presser
August; Casey P.
Claims
What is claimed is:
1. A method for managing access to data by utilizing management
information comprising a plurality of bits embedded in the data
through data transformation without changing the amount of the
data, the method comprising the steps of:
defining a plurality of sets of data regions in the data for the
plurality of bits to be embedded in the data, each of the data
regions in each set having at least one pixel and the data regions
in each set being in mutually high characteristic correlation with
each other;
comparing characteristic values between the data regions in each
set and embedding a bit of the plurality of bits in each set of
data regions by expressing the bit as a function of the
characteristic values comparison and a value of the bit;
extracting the plurality of bits of the management information
embedded in the data by comparing the characteristic values between
the data regions in the defined plurality of sets; and
managing access to said data according to said extracted management
information.
2. The method as set forth in claim 1, wherein said step for
managing the access comprises a step of changing management of
access to said data according to the type of medium for storing
said data.
3. The method as set forth in claim 2, wherein said type of medium
is ROM, RAM or R.
4. The method as set forth in any one of claims 1 through 3,
wherein said management information contains information for
controlling storage of said data, reception of said data, playback
of said data, interference of output of said data, duplication
history of said data, or modification of said management
information.
5. The method as set forth in claim 4, wherein said step for
managing the access comprises a step of, after managing the access
to said data according to said management information, embedding,
separate from said management information, additional information
for managing access to said data in said data, said management
information and said additional information managing subsequent
access to said data.
6. A system for managing access to data by utilizing management
information comprising a plurality of bits embedded in said data
through data transformation without changing the amount of data,
the system comprising:
a mechanism for defining a plurality of sets of data regions in the
data for the plurality of bits to be embedded in the data, each of
the data regions in each set having at least one pixel and the data
regions in each set being in mutually high characteristic
correlation with each other;
a mechanism for comparing characteristic values between the data
regions in each set and embedding a bit of the plurality of bits in
each set of data regions by expressing the bit as a function of the
characteristic values comparison and a value of the bit;
an extractor for extracting the plurality of bits of the management
information embedded in the data by comparing the characteristic
values between the data regions in the defined plurality of sets;
and
a unit for managing access to said data according to said extracted
management information.
7. The system as set forth in claim 6, wherein said unit for
managing access comprises a unit for changing management of access
to said data according to the type of medium for storing said
data.
8. The system as set forth in claim 7, wherein said type of medium
is ROM, RAM or R.
9. The system as set forth in any one of claims 6 through 8,
wherein said management information contains information for
controlling storage of said data, reception of said data, playback
of said data, interference of output of said data, duplication
history of said data, or modification of said management
information.
10. The system as set forth in claim 9, wherein said unit for
managing access comprises:
a unit for, after managing the access to said data according to
said management information, embedding, separate from said
management information, additional information for managing access
to said data in said data; and
a unit for managing subsequent access to said data according to
said management information and said additional information.
11. A computer program device readable by a machine, tangibly
embodying a program of instructions executable by the machine to
perform a method for managing access to data by utilizing
management information comprising a plurality of bits embedded in
the data through data transformation without changing the amount of
the data, the method comprising:
defining a plurality of sets of data regions in the data for the
plurality of bits to be embedded in the data, each of the data
regions in each set having at least one pixel and the data regions
in each set being in mutually high characteristic correlation with
each other;
comparing characteristic values between the data regions in each
set and embedding a bit of the plurality of bits in each set of
data regions by expressing the bit as a function of the
characteristic values comparison and a value of the bit;
extracting the plurality of bits of the management information
embedded in the data by comparing the characteristic values between
the data regions in the defined plurality of sets; and
managing access to the data according to the extracted management
information.
Description
FIELD OF THE INVENTION
The present invention relates to a method and system for managing
access to data by utilizing management information embedded in the
data. More particularly, it relates to embedding management
information into data through data transformation without changing
the amount of data and managing access to the data, based on this
management information, when the data is accessed.
BACKGROUND ART
With the spread of multimedia environments, systems handling
digital information, such as digital video disks (DVDS), digital
video cameras (DVCs), digital CS satellite broadcasting, and
internets, are becoming still more popular. Also, the development
of apparatuses that can process and transfer very large quantities
of multimedia data at high speed has advanced. However, it depends
upon the number of applications for attraction contents such as
theater movies whether or not the aforementioned apparatuses will
be spread from now on. No matter how excellent hardware may be, the
spread of the hardware would be difficult unless a large quantity
of contents that attracts the purchasing desire of customers are
distributed.
What becomes problematic at this time is the protection of works.
For example, digital video disks have a sufficient hardware based
method in the distribution of theater movies, however, for problems
with protection of contents, particularly with illegal duplication
(copy), there have been no methods provided such as suppliers of
contents can satisfy. This is because, although the contents of
digital data can be easily duplicated and changed, there is
provided no effective specification to prevent such action. Thus,
it is the current status that many attractive contents cannot be
expected to be distributed with these media. In fact, since such
problems with copyright have not been solved, digital video cameras
have only been sold as exclusive machines for photographing. Thus,
effectively protecting digitized works is indispensable for a
further spread of multimedia, and the development of such
protection techniques and the generation of normalized standards
have been expected.
One of conventional attempts to control duplication of digital
contents such as music is to adopt a copy generation management
system (CGMS) signal in digital audio tape (DAT). The CGMS signal
is constituted by two bits of data and represents the following
duplication conditions.
CGMS Signal Duplication Ccnditions 11 Duplication inhibition 0 No
limitations on duplication 10 One-time duplicability
The aforementioned method writes the two data bits in a
predetermined place of data format. When duplication of data is
performed, the aforementioned CGMS signal is detected at the side
of a receiver. If the content of the signal represents duplication
inhibition, the receiver stops the duplication of the content.
However, this written place can be easily specified and the content
can also be easily written over, so it is easy for users to
overwrite the content of this signal. That is, it is difficult in
the conventional technique to effectively prevent the illegal
duplication of contents because it has various disadvantages such
that
it is an approach to append data management information separate
from the data: and
it is easy to identify where is the management information.
Hence, there has been a desire for the development of techniques
that can effectively control access to digital contents and
effectively prevent illegal duplication.
DISCLOSURE OF THE INVENTION
In view of the aforementioned problems, the objective of the
present invention is to provide a system that is capable of
controlling access to data and effectively preventing illegal
access to data or the like.
To attain such objective, there is provided an access management
information embedding system for preparing management information
for managing access to data, and embedding the management
information in the data through data transformation not changing
amount of data, wherein the management information embedded through
data transformation not changing amount of data is extracted in
managing access to the data, access to the data being managed
according to the extracted management information. In addition,
management of access to the data is varied according to the type of
medium in which the data is stored such as RAM (rewritable type), R
(write once type) or ROM (read-only type). In addition, the
management information is arranged to contain information for
controlling recording of the data, reception of the data, playback
of the data, interference of output of the data, duplication
history of the data, or modification of the management
information.
Controlling recording of the data means that, when the management
information is embedded in data contained in a medium such as a
CD-ROM, the content of the CD-ROM is permitted or inhibited to be
duplicated in another medium such as a digital video disk.
Controlling reception of the data means that, when the management
information is embedded in data incoming over, for example, radio
wave or a network, the data is received by a receiver, and
permitted or inhibited to be output from the receiver.
Controlling playback of the data means that, when the management
information is embedded in data contained in a medium of a type
such as a RAM (rewritable type) or R (write-once type), the data is
permitted or inhibited to be reproduced.
Controlling interference of output of the data means that, when the
management information is embedded in data contained in a medium of
a type such as a RAM or R, the data is permitted or inhibited to be
output outside, or output interference is controlled by
superimposing noise on an output signal.
Controlling duplication history of the data means that, for
example, when the management information embedded in the data
contains information allowing duplication only once, after
duplication is performed once, additional information for
inhibiting duplication other than the management information is
added to the management information, whereby further duplication or
playback is controlled by the management information and the
additional information.
Controlling modification of the management information means that,
for example, when the management information embedded in the data
contains information allowing duplication only once, after
duplication is performed once, the management information itself is
modified to inhibit further duplication.
Although the management information relates to recording,
duplication, reception, playback, duplication history, output
interference or the like of the data, the present invention
controlling access based on the content of embedded management
information in accessing the data can be appropriately applied to
other management such as restriction on access equipment,
restriction of access users, deadline for use of data, and
authentication information without departing from the spirit of the
invention.
"Embedding" used herein means to hide specific information through
deformation of data itself by using data hiding technique or the
like. Here, data hiding is a generic term of technique for
embedding information in another medium (still image, audio, motion
image, or the like). Unlike encryption, the technique does not aim
how to hide information, but how to integrate information in a
medium in which it is embedded.
One of the important features of data hiding lies in that it is an
invisible marking technique. Since it is not to add a data bit when
information is embedded in a medium, but the information is
embedded by manipulating existing data so that it cannot be
perceived by human visual sensation (data transformation), there is
no increase in the total amount of data due to embedding of
additional information. For example, the storage side can handle
one type of medium through embedding of text or audio information
in an image. One of the other features includes indivisibility of
the embedded information. Since the data hiding directly embeds
additional information in the data structure of the medium, not in
a header or a separate file, the embedded information can be
extracted as long as the quality of the original data is saved even
if the platform of the medium or the data format is changed.
The present invention is an invention relating to a method and
system for managing access to data by utilizing management
information embedded in the data with use of such data hiding
technique or the like. It should be noted that the access
management method according to the present invention is not limited
to a specific data hiding technique, but any technique can be
utilized as is as long as it embeds information through data
transformation without changing amount of data.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram showing a procedure for recording media data on
a storage medium;
FIG. 2 is a diagram for explaining the hiding and extraction of
data employing PBC (Pixel Block Coding);
FIG. 3 is a diagram for explaining the data hiding using PBC in the
case where one pixel comprises a pixel block;
FIG. 4 is a diagram showing procedure for managing playback of data
recorded on a medium;
FIG. 5 is a block diagram of a system for managing access to data
and outputting the data;
FIG. 6 is a diagram illustrating an arrangement of pictures in
MPEG;
FIG. 7 is a diagram showing the state of macro blocks arranged in a
B picture; and
FIG. 8 is a block diagram of a data access management system
according to another embodiment.
Reference numerals and designations for major components correspond
as follows:
51 DVD-ROM 52 Reader 53 Decoder 54 Decryption unit 55 MPEG decoder
56 Management information extractor 57 D/A converter 58 Management
information modifier 59 Switch 60 Interference signal generator 61
Data supplier 62 Signal processing system 63 Output section
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a diagram showing a procedure (authoring) for recording
data on a storage medium. Data, such as images, voices, and
software, is recorded on DVD-ROM media in accordance with the
following procedure. Data that is analog data is converted to
digital data by performing analog/digital conversion processing
(step 11). This converted digital data is compressed, for example,
with a moving picture experts group (MPEG) (step 12). This
compressed data is further coded and encrypted (step 13). Finally
the media data is modulated (step 14) to be recorded on DVD-ROM
media.
In this embodiment of the present invention, data is embedded with
management information before, during or after compression, and
then is recorded on a DVD-ROM device. When systems have access to
the data recorded on DVD-ROM, the management information is used to
restrict the access to the data, and based on this management
information, systems are controlled. In this embodiment, management
information for managing duplication of data will be described as
an example. The management information represents respective status
with two-bit data, as particularly illustrated in Table 1
below.
TABLE 1 Status Contents of management information Duplication
inhibition 11 No limitations on duplication 00 (or no data)
One-time duplicabiiity 10
The embedding of management information into data is performed, for
example, between analog/digital conversion (step 11) and MPEG
compression (step 12) (or, after compression). This embedding can
be done by a technique called data hiding.
Here, a description will be made of, as an example, pixel block
coding (hereinafter referred to as PBC) which is both a method of
embedding management information which becomes an object of hiding
into certain data and conversely a method of extracting the
embedded data.
When PBC is employed, in data hiding and data extraction, data are
processed according to a predetermined conversion rule. Generally,
in a certain image, the primary characteristics, such as pixel
values of two adjacent pixels, have mutually high correlation. For
example, if there exists a "forest" area in a part of image,
adjacent pixels are in very similar green, and have mutually high
correlation. Therefore, even if these pixel values were replaced
with each other, such replacement could be little visually
perceived. That is, even if pixel values with high correlation are
manipulated according to a certain conversion rule, a degradation
would not virtually arise.
In view of this nature, one bit of data is hidden by defining as a
pixel block (i.e., a region to be embedded) an image region having
at least one pixel and also by intentionally controlling the
characteristic of an adjacent pixel block, based on a certain
conversion rule. Data is expressed by the comparison result of the
characteristics of adjacent pixel blocks. Also, when data is
extracted, it is extracted according to the extraction rule which
is determined based on this conversion rule.
Bit information is expressed by replacing the characteristic values
(e.g., brightness values) of two adjacent pixel blocks with each
other in accordance with the following conversion rule.
(Conversion Rule)
Bit 1: Case where the characteristic value of one pixel block (PB1)
is greater than that of the other (PB2)
Bit 0: Case where the characteristic value of one pixel block (PB1)
is less than that of the other (PB2)
Also, the bit information is extracted by comparing the
characteristic values (e.g., brightness values) of two adjacent
pixel blocks in accordance with the following extraction rule
corresponding to the aforementioned conversion rule.
(Extraction Rule)
Case where the characteristic value of one pixel block (PB1) is
greater than that of the other (PB2): bit 1
Case where the characteristic value of one pixel block (PB1) is
greater than that of the other (PB2) : bit 0
FIG. 2 is a diagram for explaining how the hiding and the
extraction of data are performed with the aforementioned PBC. The
pixel block PB1 or PB2 may be defined, for example, as a set of a
plurality of pixels such as 3.times.3 pixels, and it is also
possible to define a single pixel as a single pixel block. Since
adjacent pixel blocks have high correlation, image degradation
would not be felt to the extent that it could be visually
recognized, even if the positions of adjacent pixel blocks were
replaced with each other (FIG. 2(a)). Consider the case where the
positions of the pixel blocks in an original image are those shown
in FIG. 2(b). First, the characteristic values of two pixel blocks
are compared, and as the result, assume that the characteristic
value of PB1 is greater than that of PB2. When data 1 is hidden in
the original image, the characteristic values of the pixel blocks
have already satisfied the condition of the data 1 in the
conversion rule, so the characteristic values or these blocks are
not replaced with each other. On the other hand, when data is
extracted, the extraction rule has defined that the case of the
characteristic value of PB1 being greater than that of PB2 is data
1, so data 1 is extracted.
In addition, when data 0 is hidden in the original image, the
relation between the characteristic values of the pixel blocks in
the original image does not satisfy the condition of data 0 in the
conversion rule, so the characteristic values of the pixel blocks
are replaced with each other. However, this replacement cannot be
recognized visually. When data is extracted, data 0 is extracted
from the relation of the characteristic values of these blocks in
accordance with the extraction rule.
The characteristic value can employ a value related to the primary
characteristic and a value related to the secondary characteristic
of a pixel block (i.e., a region to be embedded), besides the
aforementioned brightness value. The primary characteristic is the
direct parameter of a pixel value, such as the brightness or
chromaticity of a pixel block. Also, the secondary characteristic
is obtained by resolving the primary characteristic, like a value
representative of statistical nature such as the average value or
dispersion value of the aforementioned parameters.
In addition, it is noted that pixel blocks that become objects of
PBC are not always limited to adjacent blocks. The characteristic
value of a pixel block will hereinafter be described with the
brightness value that is the primary characteristic and the
dispersion value that is the secondary characteristic, as
examples.
First, a description will be made of the case where the
characteristic value of a pixel block is taken to be a brightness
value. Since most natural images have a very high correlation
between adjacent pixels, replacing them with each other will not
result in a considerable degradation in the image. FIG. 3 is a
diagram for explaining the embedding of data of six bits in six
pixel blocks based on the aforementioned PCB in the case where 1
pixel corresponds to a pixel block.
In case where blocks containing relatively large number of pixels
are used to improve resistance against editing or compression of
images, if the brightness values of pixels are replaced with each
other between pixel blocks, noise such as stripes may occur on the
image. Hence, there is considered a method that employs a
dispersion value of the brightness of pixels as a characteristic
value.
When the nature of the brightness value of a pixel block is
resolved into an average value h and a dispersion value d, there
could be a less influence on the image in case where, in the pixel
blocks, the average value h remains the same and only the
dispersion value d is replaced than in case where the average value
is simply replaced. Therefore, it becomes possible to hide
information through the data transformation without changing amount
of data by making use of this nature, taking the characteristic
value of a pixel block to be this dispersion value d, and replacing
this dispersion value in accordance with the aforementioned
conversion rule. See Japanese Patent Application No. 8-159330.
As in FIG. 2(c), consider the case where a pixel block PB1 has an
average value h.sub.1 and a dispersion value d.sub.1 and a pixel
block PB2 has an average value h.sub.2 and a dispersion value
d.sub.2. When a bit 1 is hidden, d.sub.1 is less than d.sub.2, so
this does not satisfy the condition of bit 1 of the conversion
rule. Therefore, only the dispersion values d.sub.1 and d.sub.2 are
replaced with each other between both pixel blocks. This is
equivalent to exchanging the sizes of configurations of
distributions without changing the average values h of
characteristic values of pixels in the blocks.
Thus, the embedding of data using the aforementioned data hiding
technique, first specifies an embedding region, into which
management information is embedded, in the aforementioned data.
Then, a conversion rule where the contents of data to be embedded
is caused to correspond to the status (characteristic) of an
embedding region is made, and the status (characteristic) of the
embedding region is directly controlled according to management
information by referring to the conversion rule. By this direct
control, the management information can be embedded into the data.
By directly controlling original data, the embedding of the
management information united to the original data is performed.
Therefore, since the separation and change of only the management
information are difficult, the access management of data can be
effectively performed. Note that for the details of PBC, see
Japanese Patent Application No. 8-159330. In addition, such
techniques are comprehensively called data hiding, electronic
watermark.
The data embedded with management information with the data hiding
technique and stored on a DVD-ROM device by the aforementioned
method is accessed according to the following procedure. First,
data is read out from the DVD-ROM device. The read-out data is, as
described in connection with FIG. 1, a signal modulated (in step
14) after data embedded with management information is compressed
(in step 11) with MPEG and also after media data is coded and
encrypted (in step 12).
FIG. 4 is a diagram showing a procedure for managing the data
access method. First, data embedded with management information is
supplied to the access system. The source of data includes, for
example, storage media such as DVD-ROM and CD-R, communication such
as internet, or satellite broadcasting. The supplied data is
demodulated (in step 41) and decoded (in step 42). If the data is
MPEG compressed, it is decompressed (step 43). The management
information embedded in the data is extracted, and, if required,
the content of management information is modified, and only
required modification is embedded in the data again.
To extract management information from data input into the
recorder, the aforementioned extraction process that is one of the
data hiding methods is utilized. First, an embedding region, in
which the management information was embedded, is specified from
read-out data. Next, by referring to the extraction rule where the
status of an embedding region is caused to correspond to the
contents of data, the duplication enabling information is extracted
according to the status of the embedding region. Now, if the
extracted management information is data 00, duplication of data is
allowed according to the aforementioned rule. Also, if the
extracted management information is data 11, it means that
duplication of media data is inhibited. In this case an access
system is controlled so that duplication of data is inhibited. Data
10 means that duplication of media data is allowable under a
certain condition (only once). This means that duplication is
allowed to be generated based on data in an original DVD-ROM, but
further duplication based on the duplicated data is inhibited.
In this case an access system is controlled so that duplication of
data is allowed only once, and furthermore, it is necessary that
data is prevented from being duplicated based on the duplicated
data. Since it is important that the duplication thereafter, based
on the duplicated data from the original, is inhibited, when the
original is duplicated, duplication condition indicated by the
management information embedded in the original data is rewritten
from data 10 (one-time duplicability) to data 11 (duplication
inhibited) and then it is output as an output signal. Since the
data as this output signal is embedded with management information
indicating the condition of "duplication inhibited," data cannot be
further duplicated based on the duplicated data. In addition, there
is an option adding bits that indicates history of duplication
once. It is essential in the subsequent playback control to
determine whether it is legally copied of illegally copied.
FIG. 5 is a block diagram of a playback system for data stored on a
DVD-ROM device. The DVD-ROM device 51 on a data supply supplier 61
stores data in which management information was embedded with the
data hiding technique, as described above. The data, read out of
the DVD-ROM device 51 by a reader 52 in the data supplier 61, is
processed by a demodulator 53, a cryptograph decoder 54, and an
MPEG decoder 55, all of which constitute a signal processing system
62. As a consequence, decompressed digital data is obtained.
A management information extractor 56 specifies an embedding
region, in which management information was embedded, from the
decompressed digital data which is the output of the MPEG decoder
55 (or, directly from MPEG data), and also extracts the management
information in accordance with the status of the embedding region
by referring to an extraction rule where the status of an embedding
region is caused to correspond to the contents of data to be
extracted. A D/A converter 57 converts digitized data from which
the management information was removed to an analog signal.
Furthermore, a management information changer 58 is used to change
the content of management information as needed. (Here, it should
be noted that the management information may be extracted
regardless of before or after the MPEG decompression.)
A D/A converter 57 in the signal processing system 62 converts
digitized data from which the management information was removed to
an analog signal, and outputs an analog playback signal (e.g.,
NTSC). In addition, an interference signal generated by an
interference signal generator 60 (e.g., Analogous Protection System
(APS) such as Macrovision Signal) is selectively superimposed on
the analog playback signal by a switch 59 in an output section 63.
The switch 59 is controlled by a control signal from the management
information extractor 56. The output section 63 outputs the analog
playback signal or the superimposed signal as analog an output
signal.
In this system, the management information extractor 56 outputs a
control signal to turn off the switch 59, when the management
information extracted by the management information extractor 56
enables duplication of data. In this case, the interference signal
is not superimposed on the analog playback signal, and an analog
output signal is output as it is.
When, on the other hand, management information inhibits
duplication of data, the management information extractor 56
outputs a control signal to turn on the switch 59. In this case an
interference signal generated by the interference signal generator
60 is superimposed on the analog signal, which was output from the
D/A converter 57. When it is intended to display movie images on a
monitor based on the signal on which the interference signal is
superimposed, normal movie images can be displayed on the monitor
without being affected by the interference signal because of the
characteristics of the monitor. However, if it is intended to
record the movie images by using a digital VTR with an analog input
terminal, they are affected by the interference signal, and normal
movie images cannot be recorded. Therefore, duplication of data can
be effectively prevented because the movie images can be reproduced
from the signal superimposed with the interference signal, but they
cannot be digitized for recording.
Note that when management information is "one-time duplicability"
on the recorder, the management information changer 58 changes the
management information of read-out data to "duplication inhibited"
when it is recorded, and embeds it in the data when it is written
to a next medium. Thus, the data duplication thereafter, based on
duplicated data, can be effectively prevented.
Furthermore, in addition to the basic management information,
additional information, as particularly illustrated in Table 2
below, may be used to control copy (duplication) and playback in
more detail. This enables it to flexibly provide control depending
on the type of recording/playback medium (such as ROM, RAM or R
type).
TABLE 2 Status Manage- Addi- Playback Playback Recording ment
tional medium medium medium infor- infor- ROM type RAM type ROM
type mation mation Playback: OK Playback: NG Duplication: NG 11 0
Playback: OK Playback: NG Duplication: NG 11 1 Playback: OK
Playback: OK Duplication: OK 0 0 Playback: OK Playback: OK
Duplication: OK 0 1 N/A Playback: OK Duplication: NG 10 0 N/A
Playback: OK Duplication: NG 10 1
Zero 0 in the additional information indicates that no duplication
is performed, while 1 indicates that duplication is performed once.
In addition, N/A for the ROM type playback medium means that this
combination does not exist. That is, duplication/playback control
can be flexibly performed in more detail without erasing/modifying
the basic management information by using one-bit information
indicating whether or not duplication is performed once in addition
to information of data 11 unconditionally duplication inhibited),
10 (one-time duplicability), and 00 (unconditionally duplication
allowed). The additional information may be embedded by the same
method for the previously embedded data (management information),
or by another method to enhance security. As an alternative
embodiment, the additional information may be arranged to provide
versatile controls by using a number of bits, instead of one bit.
Anyway, it may be similarly implemented without departing the
spirit of the present invention.
In addition, the management information is not limited to
information on restriction on duplication. It is a matter of course
that the present invention is also applicable to various management
information, such as information for controlling a system. For
example, management information may also be the following playback
enabling information, as particularly illustrated in Table 3
below.
TABLE 3 Medium type = RAM Status Contents of management information
Playback inhibition 11 No limitation on playback 00 (or no data)
One-time regenerability 10
When playback enabling information enables playback of data, a
system is controlled so that playback of data is allowed. Also,
when playback enabling information inhibits playback of data, a
system is controlled so that data is not output from the system.
Besides the aforementioned information, the management information
may be a serviceable term which determines a period of time for
which media data can be regenerated or recorded, authentication
information for medium content playback, a disk key, or a title
key. Any of these pieces of information is data that becomes
necessary when data is accessed.
Another data hiding technique is described as a second embodiment.
It is noted that this embodiment is different from the
aforementioned embodiment in that the embedding of management is
performed at the time of MPEG encoding and that the extraction is
performed at the time of MPEG decoding.
Now, how embedding of management information is actually performed
in MPEG is briefly explained by referring to the data hiding
technique of Japanese Patent Application No. 8-272721 as an
example.
In MPEG, forward prediction from a past playback image, rearward
prediction from a future playback image, and bidirectional
prediction using both forward prediction and rearward prediction
are employed.
FIG. 6 is a diagram for explaining the array state of pictures in
MPEG. As shown in the figure, in order to realize bidirectional
prediction, MPEG prescribes three kinds of picture frames: an I
picture, a P picture, and a B picture.
Here, the I picture is an image processed with intra frame encoding
(intra-encoding), and all macro blocks on this picture are
processed by intra-encoding (intra frame prediction encoding). The
P picture is an image processed by forward interframe prediction
encoding, and in some cases, some of macro blocks on this picture
are processed with intra-encoding. Furthermore, the B picture is an
image processed by bidirectional interframe prediction encoding.
The macro blocks on the B picture are basically coded by forward
prediction, rearward prediction, or bidirectional prediction, but
in some cases, intra-encoding is also included. The picture screen
which is coded over the entire surface by intra-encoding is an I
picture, and the I and P pictures are coded in the same order as an
original moving picture image. On the other hand, for the B
picture, the I and P pictures are processed and then a B picture
which is inserted between the processed pictures is coded.
The embedding region in which management information is embedded is
the macro block on the B picture, and one bit of information can be
embedded into one macro block. Therefore, when message data are
multiple bits, there is the need to perform the embedding process
with respect to the macro blocks corresponding in number to the
multiple bits. FIG. 7 is a diagram showing the state of macro
blocks disposed on a B picture. The macro block is the unit that is
coded. For each macro block, movement compensation relative to a
brightness block with 16 pixels.times.16 pixels is performed, and
information compression based on a time screen correlation is
performed as an interframe prediction method using movement
compensation relative to a macro block unit.
The macro blocks on the B picture can be classified into the
following four groups as prediction types.
Intra Macro Block (Intra frame Prediction Macro Block)
The intra macro block is a macro block that is coded by only the
information about the screen itself without performing interframe
prediction.
Forward Prediction Macro Block
The forward prediction macro block is a macro block that is coded
with forward prediction by referring to the past I or P picture
(reference frame). Specifically, a square region with 16
pixels.times.16 pixels, which is most similar among the past
reference frames, is retrieved, and this macro block has
information about a prediction error (AP) which is the difference
relative to the retrieved square frame and also has information
about a spatial relative position (a moving vector). Here, the
prediction error .DELTA.P is expressed as a difference between the
brightness and the color difference obtained for 16 pixels.times.16
pixels. Note that a criterion for selecting a similar square region
depends upon encoders.
Rearward Prediction Macro Block
The rearward prediction macro block is a macro block that is coded
with rearward prediction by referring to future reference frames in
order of display. A region, which is most similar among future
reference frames, is retrieved, and this macro block has
information about a prediction error (.DELTA.N) which is the
difference relative to the retrieved region and also has
information about a spatial relative position (a moving
vector).
Bidirectional Prediction Macro Block
The bidirectional prediction macro block is a macro block that is
coded with bidirectional prediction by referring to past and future
reference frames. A region which is most similar among past
reference frames and a region which is most similar among future
reference frames are retrieved, and this macro block has
information about a prediction error ((.DELTA.N+(P)/2) which is the
difference relative to the average (per pixel) of these two regions
and also has information about a spatial relative position (two
moving vectors) between them.
To embed message data, at least one macro block, which is given an
embedding process, must first be specified in a B picture. This may
be defined, for example, as the respective macro blocks (embedding
regions) which exist between the first line and the third line of
the B picture, or it may be defined as the entire macro block of a
certain frame. In addition to the macro block being previously
defined as format in this way, it can also be determined by
employing algorithm that generates a position sequence. Note that
the algorithm for generating a position sequence can employ the
algorithm disclosed, for example, in Japanese Patent Application
No. 8-159330. Next, for the specified macro blocks that are
embedded, one bit of data is embedded into one macro block, based
on an embedding rule. This embedding rule is one where bit
information is caused to correspond to the prediction type of a
macro block. For example, there is the following rule.
(Embedding Rule) Bit information to be Interframe prediction type
of a embedded macro block Bit "1" Bidirectional prediction macro
block (represented by B) Bit "0" Forward prediction macro block
(represented by P) or rearward prediction macro block (represented
by N)
For example, consider the case where management information bits
1010 are embedded. The four bits of data are embedded in four
embedding regions disposed from the left first macro block of the
first line shown in FIG. 7 up to the fourth macro block. First, the
first data bit is a 1, so the prediction type of the leftmost macro
block (the first embedding region) is determined to be
bidirectional prediction (B) in accordance with the aforementioned
embedding rule. The prediction error in this case becomes a
prediction error which is the difference relative to the average of
a region which is most similar among past reference frames and a
region which is most similar among future reference frames. The
next data bit is a 0.
Therefore, the prediction type of the second macro block (the
second embedding region) is either forward prediction macro block
(P) or rearward prediction macro block (N) in accordance with the
embedding rule. In this case, in order to suppress image
degradation, the prediction error in the forward prediction and the
prediction error in the rearward prediction are compared to select
the type whose prediction error is smaller. In the example of FIG.
3, since the prediction error in the forward prediction is smaller
than that in the rearward prediction, the forward prediction (P) is
selected for the second macro block. Similar procedure is
repeatedly applied to the third embedding region and the fourth
embedding region.
As a consequence, the prediction type of the third macro block
becomes bidirectional prediction (B), and the prediction type of
the fourth macro block is determined to be rearward prediction (N)
because the prediction error in the rearward prediction is smaller.
In the way, the interframe prediction types of the first to the
fourth embedding regions are taken to be BPBN and four data bits
1010 (i.e., the management information 1010) are embedded in these
regions by data transformation without changing amount of data.
This is the example of embedding of management information in MPEG
using the data hiding technique described in Japanese Published
Unexamined Patent Application No. 8-272721.
Now, a description will be made of a method of extracting the
management information which was embedded in the aforementioned
procedure. In the case where management information is extracted,
information for specifying a macro block in which the management
information has been embedded must first be given. The specifying
information may be given by an outside unit. Also, it is possible
to previously embed the specifying information in data itself. In
addition, in the case where the position of an embedding region is
standardized or if an algorithm for generating a position sequence
is known, message data can be extracted. A message data extracting
method using a position sequence is disclosed in the aforementioned
Japanese Patent Application No. 8-159330, for example.
Next, from the prediction type of the specified embedding region,
the information embedded in that region is extracted by referring
to an extraction rule. This extraction rule is a rule where the
prediction type of a macro block is caused to correspond to bit
information, and this extraction rule has to be given as
information when extraction is performed. As this rule, there is
the following rule. It is noted that the corresponding relation
between prediction type and bit information in this extraction rule
is the same as that of the aforementioned embedding rule.
(Extraction Rule) Bit information Interframe prediction type of a
macro block to be extracted Interframe prediction type of a macro
block Bit "1" Interframe prediction type of a macro block Forward
prediction macro block (represented Bit "0" by P) or rearward
prediction macro block
A description will be made of the case where management information
has been embedded as shown in FIG. 7. As previously described,
management information bits have been embedded as a premise in the
embedding regions from the left first macro block of the first line
shown in FIG. 3 up to the fourth macro block. Because the
prediction type of the leftmost macro block is bidirectional
prediction (B), bit 1 is extracted by referring to the
aforementioned extraction rule. The prediction two of the second
macro block is forward prediction (P), so bit 0 is extracted
according to the extraction rule. By repeatedly applying the same
procedure to the other macro blocks, bit 1 and bit 0 are extracted
in sequence. As a consequence, management information bits 1010 are
extracted from these regions.
According to this embodiment, the prediction type of a macro block
and an embedded bit are determined so that they are caused to
correspond with each other, when a moving picture image is coded.
Therefore, management information can be embedded in the moving
picture image without substantially having an influence on the
compression efficiency of the moving picture image and also without
substantially causing a degradation in the picture quality. In
addition, it is very difficult to remove the management information
embedded in this way from the moving picture image. Furthermore,
since an amount of information to be embedded is almost independent
of the contents of an image, it is possible to efficiently embed
message data.
As will be seen from the foregoing description, the feature of the
present invention resides in that management information is
embedded in data by using the data hiding technique or the like,
which embeds data through data transformation without changing
amount of data, and, when the data is accessed (regenerated or
recorded), a system for managing access to the data is controlled
based on the management information. Therefore, the present
invention is not limited to the aforementioned data hiding method
and it is noted that the present invention is applicable to a
variety of methods.
Finally, a description will be made of a data access system shown
in FIG. 8. While the aforementioned management information
represents three statuses with two bits, an embodiment described
here is intended to substantially provide three statuses for the
system with one-bit management information. To this end, the system
of the embodiment comprises a controller 81 that detects in what
state data is supplied to the system, and controls output of the
system according to the state. A data supply unit 82 is to supply
data embedded with management information to the access system, and
includes, for example, an optical system for reading data from
DVD-ROM, and a circuit for capturing data on the internet into the
system. Here, the management information is represented by one-bit
information respective bit of which indicates the following
information.
TABLE 4 Management Information Status Contents of management
information Duplication inhibited 1 Duplication allowed 0
Data supplied from the data supply unit 82 is processed by a signal
processing system 83 that performs demodulation, decryption, D/A
conversion or the like. A management information extractor 84
specifies an embedding region in which management information is
embedded from the data obtained through processing by the signal
processing system 83, and extracts the management information
according to the state of an embedding region by referring to an
extraction rule in correspondence with content of data for
extracting the state of the embedding region. The management
information extractor 84 outputs a control signal according to the
extracted information. The control signal is for controlling an
output unit 85, superimposes an interference signal selectively
generated by an interference signal generator 86 according to the
content of the control signal on the output signal, and outputs
them. That is, when the management information is bit 0
(duplication allowed), a switch in the output unit 85 is turned off
to output the data. On the other hand, when the management
information is bit 1 (duplication inhibited), the switch is turned
on to superimpose an interference signal on the data, and to output
them. Since the operation is substantially same as that of the
components of the system shown in FIG. 5, no further detail is
described.
A controller 81 connects to the data supply unit 82, and monitors
in what state the data is supplied to the system. Then, even when
the management information is bit 0, or allows duplication of the
data, the controller 81 controls the output unit 85 so that the
switch in the output unit 85 is turned on depending on the result
of supply state to output a superimposed signal. That is,
duplication of data is forcedly inhibited, although the management
information itself allows duplication of the data.
A specific data supply state is determined by monitoring, for
example, "when data is captured into an access system through a
recording medium, in duplication, whether the loaded recording
medium is a read-only type or a rewritable type." The type of
recording medium can be easily determined since it can be
recognized in an untamparable area (lead-in area) of the recording
medium by the system through hardware. When it is intended to
perform duplication of data in a state where the data is being
supplied from a read-only recording medium, the controller 81 would
not forcedly turn off the switch. Thus, the access system operates
after the extracted management information, and data can be
duplicated as long as the management information allows the
duplication. On the other hand, when it is intended to duplicate
data in a state where the data is being supplied from a rewritable
recording medium, the controller 81 turns on the switch regardless
of the content of management information. Thus, data cannot be
duplicated from the rewritable recording medium.
Generally, when famous or important content is prevented from
illegal duplication or tampering, a supplier of content stores and
distributes it in a ROM. Therefore, the supply state in ROM state
means that the data can be considered to be original, rather than
duplicated data. On the other hand, when data is supplied as a RAM
or R, in most cases, the data can be considered to be duplicated
data already duplicated in the RAM or R. Therefore, as long as the
data stored in a ROM is considered to be original, and that in a
RAM or R is considered to be duplicated data, further duplication
of duplicated data, or illegal duplication can be effectively
prevented by providing such function in the system. Consequently,
even with the one-bit management information that can represent
only two status of "duplication allowed or inhibited," the system
determines whether or not data is original according to its supply
state, so that a third status of "one-time duplicability" can be
substantially provided for the system.
Since the management information to be embedded can be represented
by one bit, instead of two bits, it becomes unnecessary to take
sequence of bit arrangement into account rather than the size of
management information. If the content of information differs for
the arrangement of bits 01 and 10 when the management information
is of two bits, it is necessary to take their sequence into account
in extracting the information. However, if it is of one bit, it is
not necessary. Therefore, significant improvement is provided for
accuracy in extraction of information.
The supply state to be monitored may include a case, "When data is
captured through communication or broadcasting, whether or not an
access system is connected to a network in duplication" in addition
to the aforementioned case. In this case, if data is connected to
the network in duplication, the data is considered to be original.
However, if data is not connected to a network in duplication, it
is considered to be duplicated data further duplicated from
duplicated data stored in a location other than the network (e.g.,
a ROM in the own system). Therefore, for the 10 duplication through
a network, it is sufficient to allow duplication under a condition
that data is connected to the network. Furthermore, various
approaches may be contemplated including monitoring when data is
being supplied.
APPLICABILITY IN INDUSTRY
As described above, a supplier embeds an access condition for a
receiver of content to be supplied as management information in the
content itself, and distributes the content to general public. An
access system, which receives the content, contains a function
therein that extracts the management information embedded in the
content, and controls access to the content according to the access
condition defined by the management information. Therefore, the
receiving system can effectively inhibit access to the content by
the receiver, particularly illegal duplication of the content by
the receiver.
* * * * *